Support V4L2 fourcc values

[dcz-self]

FourCC has uses outside of DRM, like in V4L. Currently drm-fourcc has IMO the best infrastructure for printing and conversions, but it's not useful for V4L because of the missing formats (see this comment.

It would be great if other use cases for FourCC could take advantage of what this project made.

How about we added the missing V4L formats to this library?

We could either add all known formats into the same type, or create separate types, one for DRM and one for V4L.

If I contributed that, would it be accepted?